1. Field of the Invention
The present invention relates to hair drying apparatus of the type that are designed to be hand held, and which produce a flow of hot air without requiring the dryer to be connected to an external A/C power source to operate. In particular, the present invention is directed to improvements in such handheld cordless hair dryers which will serve to make a hair dryer produced in accordance with the invention lighter, safer, more compact, and more convenient to use than previously existing hair dryers of this type.
2. Description of Related Art
The overwhelming majority of handheld hair dryers in use today are of the type which must be connected to an external A/C power source via an electrical connector cord. The electrical power derived from the A/C power source is used to heat electrical heating coils, across which a flow of air is directed by a blower. Because such hair dryers have a power requirement of as much as 600 to 1200 watts, they are not suitably adaptable to "cordless" usage because it is not feasible to meet this power requirement via a D.C. power supply (such as storage batteries) in a device intended to be held comfortably in one hand.
Therefore, to obtain a handheld hair dryer that does not have its portability tied to the length of its electrical power cord, handheld hair dryers have been developed which use a gas or liquid fueled combustion device to heat the flow of drying air. One example of a cordless handheld hot air hair dryer of this type is that of Bourdeau U.S. Pat. No. 4,635,382. The dryer of the Bourdeau patent is provided with a fuel reservoir for storing a vaporizable fuel in a liquid state and the fuel is vaporized and combusted within a heating chamber disposed in a nozzle portion of the dryer. The heating air flow is generated by a battery powered motor that is used to drive the fan, and a single manually operated control means is used to control both the amount of current applied to the fan motor and to adjust the flow of fuel to the combustion device. This manually operated control means utilizes a slide-type actuator to move a rheostat for the fan motor and a valve of a fuel supply line.
However, the hair dryer of the above-noted patent provides no means for preventing the combustion fumes from being mixed with and discharging along with the heating air, nor are there are safeguards to protect against overheating conditions or failure of the combustion device to ignite. Likewise, the fact that the dryer contains a reservoir of liquid fuel poses a significant safety hazard, as does the fact that, once the actuating member of the manually operative control means is shifted into its "on" position, it remains in its operational state, even if the user should not be holding the device at the time, having put it down without turning it off. Finally, the heater of the device employs asbestos which is hazardous, and the unit incorporates a recharging transformer in the handle which both adds weight to the unit as well as placing an electrical component close to the reservoir of ignitable fluid.
Another patent disclosing a cordless handheld hair drying apparatus is that of the Raccah, et al. U.S. Pat. No. 4,555,232. The Raccah, et al. patent discloses several different dryer constructions. In accordance with aspects of each of these embodiments, various of the above-noted deficiencies are overcome. For example, in one embodiment, instead of utilizing a liquid fuel reservoir, a gas-containing fuel cartridge is placed within the handle portion of the dryer. Additionally, a flame detector is provided to shut off the gas supply in the event of a flame failure and a temperature sensing means is provided in another embodiment whereby a valve progressively closes as the temperature in the vicinity of the burner increases, thereby decreasing the supply of fuel to the burner and acting to prevent a temperature overload. Furthermore, while this patent discloses that steps may be taken to prevent combustion products from entering the air flow, via ducts or shrouds, no particular arrangement for achieving such a result is described. Still further, all of the embodiments disclosed in the Raccah, et al. patent are relatively complex in construction and they fail to provide an arrangement whereby heat output can be maximized without overheating the nozzle body portion of the dryer.
Thus, there is still a need for a compact, cordless handheld hair dryer which can be produced in a simple and, therefore, less costly manner, yet still maximizes safety and heat output efficiency.